A telephone network is generally formed by a number of interconnecting switches at service switching points (SSP); these provide basic routing for telephone messages and also some other advanced features. One such feature is the capability for playing `network information` messages to a caller without creating a billing record, for example--`your call is being redirected. Please hold while we reroute your call`. However, switches have a major disadvantage in that it is difficult to record and manage network information or service messages. As such it presents problems for administrators implementing new services. Also switches are not flexible when it comes to the addition of new features or services. The high capacity computers used in a telephony network are well known in the art. See, eg. `Intelligent Networks Basic Technology, Standards and Evolution` by T. Magedanz et al 1996, International Thomson, incorporated herein by reference.
Network information messages are much easier recorded and managed in an Intelligent Peripheral than in the switches where they have been historically resident. Also Intelligent peripherals have increased flexibility when it comes to the creation of new services or features to the telephone network. The switch transfers the call to the IP (14) so that the message can be played. Before it can be played the IP (14) has to acknowledge to the switch that it has accepted the call by sending an event using a common protocol with the switch. The switch interprets this acknowledgement to mean that the call has been accepted and that a billing record should be created and charged to the caller. This is quite a large restriction for network services.
A typical (ISDN) system comprises an SSP (10), a controller (12) (SCP--service control point) and an IP (14) with an ISDN connection between SSP (10) and IP (14) (see FIG. 1). The controller is typically a computer server having a database with a number directory and instructions for forwarding calls to certain IPs. The controller is connected to the SSP (10) via a Signalling System No.7 (SS7) link and the IP (14) by standard computer links. A telephone (16) is connected to the SSP (10) either by an ISDN Basic rate interface for an ISDN telephone or an analogue connection for a standard telephone. An ISDN telephone is used, as shown in the examples.
A common operation for such a system is a call to an enhanced network service like an 0800 number when the service is not available from telephone (16). The operation proceeds as follows--a setup message is sent from the telephone (16) to the SSP (10) which sends a message back to the caller to indicate that the call is proceeding. At the same time the SSP (10) detects that this is an enhanced service number and sends a connection query to the SCP (12). On receipt the SCP (12) sends a message back to the SSP (10) along with routing information for the particular IP (14) that is to be used for the `service not available` application. At the same time call information is sent to the IP (14) over the TR1129+ connection from the SCP so that it can prepare for a connection with the SSP (10). The SSP (10) then sends a message to the IP (14) requesting a call be set up. At the IP (14) the `service not available` application is selected. An AnswerCall action is executed which causes a message to be sent to the SSP (10) to indicate the call is in progress, an optional alert message can be sent to the SSP (10) and then a connect message requesting connection with the SSP (10). On receipt of the connect message from the IP (14) the SSP (10) creates a billing record and along with a connect message to the caller, connects a voice channel between the IP (14) and the caller. Once the voice channel is open the IP (14) plays the voice message to the caller. All this time the billing record is charging for the time that the voice channel is connected. At the end of the voice message the IP (14) ends the call by sending a disconnect message to the SSP (10) which stops charging for the call by closing the billing record and sends a disconnect message to the caller.
There is a need for intelligent peripheral services to be provided that interact with the caller but do not create billing records in the network and therefore do not charge the caller. There is also a need for intelligent peripheral services which have some initial interaction with the customer on a no charge basis, but then move on to a different part of the service and wish to charge the customer.